The present invention relates to a film of a trimethylene-2,6-naphthalene dicarboxylate (co)polymer comprising a 2,6-naphthalene dicarboxylic acid component and a 1,3-propanediol component, a sulfonic acid quaternary phosphonium salt copolymer and a composition thereof.
Polyethylene terephthalate (may be abbreviated as PET hereinafter) is widely used as molded products such as films exemplified by magnetic recording tapes, capacitors, ink ribbons and thermally shrinkable labels for PET bottles, sheets exemplified by trays, hollow containers and cover materials thereof, and PET bottles thanks to its excellent mechanical and chemical properties as a material.
However, PET is not satisfactory yet in terms of gas barrier properties against oxygen and carbon dioxide though it is superior to polyethylene and polypropylene. The further improvement of gas barrier properties of PET is desired when it is used to wrap contents which are easily oxidized, such as food containing oil, and when it must prevent the leakage of filled gas like carbonated drinks.
To improve the gas barrier properties of PET, there are known methods of coating or laminating a resin having higher gas barrier properties than PET, such as polyvinylidene chloride, ethylene-vinyl acetate copolymer saponified product or polyamide. These resins have poor adhesion to PET, thereby causing delamination, whereby a container loses its transparency, and a laminate consisting of different types of polymers is disadvantageous from the viewpoint of recovery.
There are proposed a method of using a polymer obtained by substituting part or all of the terephthalic acid component of PET with isophthalic acid in place of PET (JP-A 59-64624) (the term xe2x80x9cJP-Axe2x80x9d as used herein means an xe2x80x9cunexamined published Japanese patent applicationxe2x80x9d) and a method of improving gas barrier properties by copolymerizing 1,3-phenylene dioxydiacetic acid or the like (JP-A 60-501060). Both methods involve such problems that satisfactory gas barrier properties are not achieved, a reduction in glass transition temperature (Tg) is large and heat resistance deteriorates.
An ethylene-vinyl acetate copolymer (to be abbreviated as EVOH hereinafter), polyamides (to be abbreviated as PA hereinafter) and polyvinylidene chloride (to be abbreviated as PVDC hereinafter) are used as polymers having higher gas barrier properties than the above polyester. However, the gas barrier properties of EVOH and PA greatly depend upon humidity and deteriorate at a high humidity. PVDC may generate a poisonous gas such as dioxin when it is burnt.
PET films and PA films are widely used for packing as a film having high piercing strength and high piercing resistance. However, as these films have high tear strength, when they are used in a wrapping bag and their contents are to be taken out from the wrapping bag, the bag cannot be easily ripped open and it takes time to take out the contents.
To provide tearability to a film, the end of the film is notched or slit, or an uniaxially stretched film of a polyamide or polyolefin is used as an inner layer and laminated with a polyester to produce a film. These methods boost costs, disadvantageously. It is desired that a film itself should have tearability if possible.
Thus, a film which is easily torn while it has high piercing strength is unknown. If a film having both piercing resistance and tearability is obtained, it is expected to be used in a wide range of fields including packing materials.
Poly(methylene-2,6-naphthalene dicarboxylate) itself is disclosed by JP-B 43-19108 (the term xe2x80x9cJP-Bxe2x80x9d as used herein means an xe2x80x9cexamined Japanese patent publicationxe2x80x9d) which discloses a composite filament or composite staple fiber and the other polyester thereof which is produced in the presence of a polymer comprising trimethylene dinaphthalate as a polymerization unit, that is, a mixture of poly(trimethylene dinaphthalate), poly(trimethylene-2,6-dinaphthalate)Mn(OAc)2 and Ti(OBu)4 as a catalyst and which has a relative viscosity of 0.67.
It is an object of the present invention to provide a film of an aromatic polyester which is superior in gas barrier properties to PET out of polyesters having excellent features that they have small humidity dependence and that they do not generate a poisonous gas when they are burnt.
It is another object of the present invention to provide an aromatic polyester film which is easily torn while it has high piercing strength.
It is still another object of the present invention to provide a film having excellent features which has gas barrier properties equivalent to those of a polyamide film, does not experience an increase in moisture permeability unlike a polyamide film and a reduction in gas barrier properties at a high humidity and does not generate a poisonous gas when it is burnt.
It is a further object of the present invention to provide an aromatic polyester which has excellent adhesion to a rotary cooling drum, and excellent productivity and sanitation because it suppresses the contamination of an electrostatic wire and the adhesion of a sublimate to an extrusion nozzle in the production of a film.
It is a still further object of the present invention to provide an aromatic polyester which decreases the amount of a component eluting from a polyester film without reducing the production efficiency of a film in the production of the film and is suitable for use in packages, especially food packages.
It is a still further object of the present invention to provide an aromatic polyester which can decrease the amount of an oligomer eluting from a polyester film without reducing the production efficiency of a film in the production of the film.
It is a still further object of the present invention to provide an aromatic polyester which has a small content of foreign matter and is excellent in color, moldability, light resistance and gas barrier properties in the production of a film.
It is a still further object of the present invention to provide an aromatic polyester which gives a film having excellent antifungal properties.
It is a still further object of the present invention to provide a laminated polyester film having a primer layer which is excellent in gas barrier properties, heat resistance, water resistance, anti-block properties and adhesion.
Other objects and advantages of the present invention will become apparent from the following description.
According to the present invention, firstly, the above objects and advantages of the present invention are attained by an aromatic polyester film, (1) which comprises an aromatic polyester comprising 2,6-naphthalenedicarboxylic acid as the main dicarboxylic acid component and 1,3-propanediol as the main diol component and (2) having a density of at least 1.310 g/cm3.
Secondly, the above objects and advantages of the present invention are attained by a laminated polyester film comprising the above aromatic polyester film of the present invention and another polyester layer existent on at least one side of the film.
Thirdly, the above objects and advantages of the present invention are attained by an aromatic polyester which comprises 2,6-naphthalenedicarboxylic acid as the main dicarboxylic acid component and 1,3-propanediol as the main diol component and a sulfonic acid quaternary phosphonium salt having an ester forming functional group in an amount of 0.1 to 45 mmol % based on the total of all the dicarboxylic acid components.
In the fourth place, the above objects and advantages of the present invention are attained by a polyester composition which comprises the above aromatic polyester of the present invention in an amount of 60 wt % or more and another aromatic polyester in an amount of 40 wt % or less based on the total of the aromatic polyester and the another aromatic polyester.
In the fifth place, the above objects and advantages of the present invention are attained by an antifungal polyester composition which comprises any one of the aromatic polyester of the present invention and the above aromatic polyester composition of the present invention and an inorganic anti-fungus agent in an amount of 0.1 to 10 wt % based on the above aromatic polyester of the present invention or the aromatic polyester composition of the present invention.
The present invention will be described in detail hereinafter. A description is first given of the aromatic polyester film of the present invention.
As described above, the aromatic polyester film of the present invention, (1) which comprises an aromatic polyester comprising 2,6-naphthalenedicarboxylic acid as the main dicarboxylic acid component and 1,3-propanediol as the main diol component and (2) which has a density of at least 1.310 g/cm3.
In the above aromatic polyester (1), the 2,6-naphthalenedicarboxylic acid as the main dicarboxylic acid component and the 1,3-propanediol as the main diol component are contained in an amount of preferably 80 mol % or more, more preferably 85 mol % or more, much more preferably 90 mol % or more based on the total of all the dicarboxylic acid components and the total of all the diol components, respectively.
In the present invention, dicarboxylic acid components other than 2,6-naphthalenedicarboxylic acid include dicarboxylic acids such as terephthalic acid, isophthalic acid, succinic acid, adipic acid, sebacic acid, phthalic acid, 2,7-naphthalenedicarboxylic acid and 1,4-naphthalenedicarboxylic acid, and ester derivatives thereof. Out of these, terephthalic acid, isophthalic acid and ester derivatives thereof (such as dimethyl terephthalate and dimethyl isophthalate) are preferable. These dicarboxylic acids may be used alone or in combination of two or more. The total amount of dicarboxylic acid components other than 2,6-naphthalenedicarboxylic acid is preferably less than 20 mol % based on the total of all the dicarboxylic acid components in order not to impair the feature of the present invention. It is more preferably less than 15 mol %, particularly preferably less than 10 mol %.
In the present invention, diol components other than 1,3-propanediol include aliphatic glycols such as ethylene glycol, 1,2-propanediol, tetramethylene glycol, hexamethylene glycol, neopentyl glycol, cyclohexane dimethanol and octamethylene glycol; alicyclic glycols such as 1,4-cyclohexane dimethanol; aromatic diols such as bisphenol S, bisphenol A and hydroquinone; and high-molecular glycols such as polyethylene glycol and polypropylene glycol. These diol compounds may be used alone or in combination of two or more. The total amount of diol components other than 1,3-propanediol is less than 20 mol %, preferably less than 15 mol %, more preferably less than 10 mol% based on the total of all the diol components in order not to impair the feature of the present invention.
The above aromatic polyester may contain a component derived from an oxycarboxylic acid such as an aromatic oxyacid exemplified by hydroxybenzoic acid or aliphatic oxyacid exemplified by xcfx89-hydroxycaproic acid in an amount of less than 20 mol % or a polycarboxylic acid such as trimellitic acid or pyromellitic acid or a polyol such as pentaerythritol in a small amount, for example, 3 mol % or less based on the total of all the dicarboxylic acid components if it does not impair the effect of the present invention.
The aromatic polyester in the present invention is particularly preferably a homopolymer consisting of 2,6-naphthalenedicarboxylic acid as a dicarboxylic acid component and 1,3-propanediol as a diol component, or a copolymer comprising, as a copolymerized component, at least one compound selected from the group consisting of dicarboxylic acids other than 2,6-naphthalenedicarboxylic acid and diols other than 1,3-propanediol in an amount of 30 mol % or less based on the total of all the dicarboxylic acid components.
This copolymer can be a copolymer comprising, as a copolymerized component, a sulfonic acid quaternary phosphonium salt having an ester forming functional group in an amount of 0.1 to 45 mmol % based on the total of all the dicarboxylic acid components. This copolymer has excellent adhesion to a rotary drum and suppresses the contamination of an electrostatic wire and the adhesion of a sublimate to an extrusion nozzle in the production of a film.
The polyester in the present invention is substantially linear and has film formability, particularly film formability by melting.
Further, the aromatic polyester of the present invention may contain additives such as a crystal nucleating agent, stabilizer, dye, lubricant, ultraviolet absorber, antioxidant, optical bleaching agent, hard coating agent, dispersant and flame retardant as required.
The aromatic polyester of the present invention may be produced by any conventionally known method.
For example, an ester exchange reaction between an ester derivative such as a dimethyl ester or diethyl ester of 2,6-naphthalenedicarboxylic acid and an aliphatic glycol is carried out by heating in the presence of at least one of compounds containing sodium, potassium, magnesium, calcium, zinc, strontium, titanium, zirconium, manganese or cobalt as a conventionally known ester exchange catalyst and then polymerization is carried out by heating in the presence of a polymerization catalyst under reduced pressure to produce an aromatic polyester. Preferred examples of the polymerization catalyst include antimony compounds, germanium compounds and titanium compounds.
The aromatic polyester of the present invention can also be obtained by the direct polymerization of a dicarboxylic acid and a glycol which is a known method similar to the direct polymerization of PET.
After melt polymerization, the aromatic polyester may be chipped and solid-phase polymerized. A polyester having a higher intrinsic viscosity can be easily obtained by solid-phase polymerization and a film having excellent mechanical strength can be obtained therefrom.
It is desired from the viewpoint of moldability that the aromatic polyester of the present invention should have an intrinsic viscosity measured at 25xc2x0 C. in an o-chlorophenol solvent of 0.4 to 1.5, preferably 0.5 to 1.3. When the intrinsic viscosity is lower than 0.4, the formed film has poor strength disadvantageously. A polyester having an intrinsic viscosity of more than 1.3 is not preferred because filtration and extrusion molding become difficult when it is molded.
The aromatic polyester film of the present invention includes an unstretched film obtained by extruding a molten polymer from a die or the like and by heating and an uniaxially or biaxially oriented film obtained by stretching the film in a uniaxial or biaxial direction sequentially or simultaneously to orient molecular chains.
Generally speaking, the gas barrier properties of a polymer are connected with the cohesive energy density of polymer molecular chains, free volume fraction indicative of a gap between polymer molecular chains, crystallinity and the degree of orientation of molecular chains. As for the relationship between gas barrier properties and crystallinity out of these, it is said that gas molecules such as oxygen and carbonic acid gases penetrate only amorphous portions of a polymer and not crystal portions. That is, when polymers of the same type are compared with each other, a polymer having higher crystallinity has higher gas barrier properties due to fewer portions which can breathe.
As for the relationship between the degree of orientation and gas barrier properties, the gap between molecular chains becomes smaller as the molecular chains are oriented by stretching rather than in a random state, thereby making it more difficult to transmit gases. When polymers of the same type are compared with each other, a polymer with a higher draw ratio has higher gas barrier properties.
The density of the aromatic polyester film of the present invention is at least 1.310 g/cm3, preferably at least 1.320 g/cm3. The density is an index indicative of crystallinity. When polymers of the same type are compared with each other, a polymer with higher crystallinity has higher density. Therefore, for the above reason, gas barrier properties improve as density increases. The density is preferably 1.366 g/cm3 or less. When crystallinity is too high, gas barrier properties improve but tenacity is lost when a polymer is formed into a film or the like, disadvantageously as practical use.
A stretched film formed from the aromatic polyester of the present invention is preferred because it has higher gas barrier properties than an unstretched film formed therefrom for the above reason.
The biaxially oriented aromatic polyester film of the present invention preferably has a total of Young""s moduli in two crossing directions on the film plane of 350 to 1,300 kg/mm2. When the total of Young""s moduli is below the above range, the strength of the film becomes insufficient when in use. The total of Young""s moduli is more preferably 400 kg/mm2 or more, much more preferably 500 kg/mm2 or more. The film having a total of Young""s moduli of more than 1,300 kg/mm2 is not preferred because its delamination resistance deteriorates. The total of Young""s moduli is preferably 900 kg/mm2 or less, more preferably 800 kg/mm2 or less.
The biaxially oriented aromatic polyester film of the present invention has a total of breaking strengths in two crossing directions on the film plane of 30 kg/mm2 or more. When the total of breaking strengths is below that range, the strength of the film becomes insufficient when in use. The total of breaking strengths is more preferably 40 kg/mm2 or more, much more preferably 50 kg/mm2 or more.
The plane orientation coefficient (ns) of the biaxially oriented aromatic polyester film of the present invention is preferably 0.02 to 0.3. When the plane orientation coefficient is smaller than 0.02, the strength of the film becomes insufficient disadvantageously. When the plane orientation coefficient is larger than 0.3, the delamination resistance of the film deteriorates disadvantageously. The plane orientation coefficient is more preferably 0.10 to 0.30.
The biaxially oriented aromatic polyester film of the present invention preferably has a ratio of piercing strength to tear strength (piercing strength/tear strength) of 4 or more when it is a 15 xcexcm thick film.
A film for packing must have high piercing strength and low tear strength at the same time. When the film has a large ratio of piercing strength (film pierced strength by a needle with an end portion of 0.5 mm in diameter when it pierces the film at a rate of 50 mm/min) to tear strength (force required for tearing a film per unit thickness) both of which will be defined in the section of Examples, the film can be evaluated as a film having high piercing strength and low tear strength at the same time.
The ratio (of piercing strength/tear strength) is preferably 7.0 or more, more preferably 10.0 or more. When the ratio is smaller than 4, tear strength becomes too high as compared with piercing strength, thereby making it difficult to obtain sufficient piercing resistance and tearability.
The tear strength is particularly preferably 0.25 kg/mm or less.
The biaxially oriented aromatic polyester film of the present invention preferably has a haze of 20% or less to achieve such transparency that its contents can be seen when it is used as a packing material. In order to adjust the haze to less than 20%, stretching and heat treatment conditions are selected to prevent crystallinity from becoming too high and further the amount of inert fine particles added to provide slipperiness to the film is controlled not to become too excessive.
The haze is more preferably 0.01 to 15%, much more preferably 0.03 to 10%.
The aromatic polyester film of the present invention preferably has an oxygen permeability constant at 20xc2x0 C. and a relative humidity of 90% of 22xc3x9710xe2x88x9213 (ccxc2x7cm/cm2/sec/cmHg) or less.
When the oxygen permeability constant is larger than 22xc3x9710xe2x88x9213 (ccxc2x7cm/cm2/sec/cmHg), oxygen barrier properties at a high humidity are low. The oxygen permeability constant at 20xc2x0 C. and a relative humidity of 90% is more preferably 15xc3x9710xe2x88x9213 (ccxc2x7cm/cm2/sec/cmHg) or less.
Further, the aromatic polyester film of the present invention preferably has an oxygen permeability constant at 20xc2x0 C. and a relative humidity of 65% of 22xc3x9710xe2x88x9213 (ccxc2x7cm/cm2/sec/cmHg) or less.
The aromatic polyester film of the present invention has a moisture permeability at 20xc2x0 C. and a relative humidity of 90% of 30 (g/m2/24 hr) or less when it is a 12 xcexcm thick film.
As the value of moisture permeability increases, water-vapor barrier properties lower, thereby making it difficult to use it to pack contents which are apt to be easily damaged by water vapor, such as dried food. The moisture permeability is preferably 25.0 (g/m2/24 hr) or less, more preferably 20.0 (g/m2/24 hr) or less.
The aromatic polyester film of the present invention preferably has a breaking elongation retention of 50% or more after 150 hours of irradiation at a temperature of 60xc2x0 C. with a sunshine weatherometer. When the breaking elongation retention is smaller than 50% and the film is exposed to the sunlight for a long time, the film readily becomes defective. The breaking elongation retention is more preferably 60% or more, much more preferably 70% or more.
The aromatic polyester film of the present invention preferably has a transmission of ultraviolet light having a wavelength of 360 nm of 40% or less. When the ultraviolet transmission is more than 40% and the film is used to pack food, the film may modify contents disadvantageously. The ultraviolet transmission is more preferably 30% or less, much more preferably 20% or less.
Preferably, the aromatic polyester film of the present invention has an extractability treated with ion exchange water at 125xc2x0 C. for 1 hour of 0.0155 mg/cm2 or less. The film showing this extractability can be suitably used for packing, especially packing foods.
More preferably, the aromatic polyester film of the present invention has an oligomer extractability with chloroform of 0.15 wt % or less.
The aromatic polyester film of the present invention may contain a small amount of inert fine particles to provide slipperiness to the film. Examples of the inert fine particles include inorganic particles such as spherical silica, porous silica, calcium carbonate, silica alumina, alumina, titanium dioxide, kaolin clay, barium sulfate and zeolite; and organic particles such as silicone resin particles, crosslinked polystyrene particles and polypropylene particles. The inert particles may be natural or synthetic. Inorganic particles are preferably synthetic rather than natural because they are uniform in diameter. The crystal form, hardness, specific gravity and color of the inert fine particles are not particularly limited.
The average particle diameter of the above inert fine particles is preferably in the range of 0.05 to 5.0 xcexcm, more preferably 0.1 to 3.0 xcexcm. When the average particle diameter is smaller than 0.05 xcexcm, it is difficult to provide sufficient slipperiness and when the average particle diameter is larger than 5.0 xcexcm, the surface of the film tends to become uneven.
The content of the inert fine particles is preferably 0.001 to 1.0 wt %, more preferably 0.03 to 0.5 wt %. When the content is smaller than 0.001 wt %, it is difficult to provide sufficient slipperiness and when the content is larger than 1.0 wt %, the transparency of the film or sheet is apt to lower.
The inert fine particles added to the film may be composed of one component, two components or multiple components selected from the above examples.
The time of adding the inert fine particles is not particularly limited if it is before or during film formation. The inert fine particles may be added in a polymerization stage or when the film is formed.
Particularly preferably, the inert fine particles are supplied to a vented double-screw kneading extruder to be kneaded as a dispersion containing the inert fine particles dispersed in water and/or an organic compound having a boiling point lower than the melting point of the polyester resin.
Water and/or an organic compound having a boiling point lower than the melting point of the thermoplastic resin are/is used as a medium for the dispersion. Water, methanol, ethanol, ethylene glycol and the like are preferred from an economical point of view and the viewpoint of handling properties. Water is the most preferred medium from the viewpoint of safety.
How to supply the dispersion containing the inert fine particles to the vented double-screw kneading extruder is not particularly limited if it is efficient, safe and quantity determinative and does not affect dispersibility. At least one of vent holes is preferably kept under reduced pressure to remove water and/or the organic compound having a boiling point lower than the melting point of the thermoplastic resin. The vent hole is preferably kept at 100 Torr or less, more preferably 50 Torr or less, much more preferably 30 Torr or less. Otherwise, dispersibility becomes unsatisfactory.
The aromatic polyester film of the present invention preferably has a thickness of 400 xcexcm or less when it is a biaxially oriented film. A film having a thickness of more than 400 xcexcm after stretching is not preferred for such production reasons that it is difficult to stretch the film because it is too thick and heat hardly reaches the inside of the film when it is heat set. The biaxially oriented film has a thickness of more preferably 350 xcexcm or less, the most preferably 250 xcexcm or less.
The aromatic polyester film of the present invention may be produced by a general method for producing a PET or polyethylene 2,6-naphthalene dicarboxylate (may be abbreviated as PEN hereinafter) film, for example, supplying a polyester raw material to the hopper of a single screw or double screw extruder connected to a T die or I die through a gear pump, melting it in the cylinder of the extruder, extruding it into a sheet form from the die, and cooling it with a casting roll. As for the casting roll, the formed sheet is preferably brought into close contact with the casting roll using an electrostatic adhesion device or air knife to prevent thickness nonuniformity and the inclusion of air.
The aromatic polyester film of the present invention may be produced by conventionally known film production methods which have been used for thermoplastic resins. The methods include, for example, extrusion molding using a T die or I die, inflation extrusion molding using a looped die, cast molding, calender molding, press molding and the like. Any one of uniaxial stretching and biaxial stretching using a roll or tenter which is generally used to form a PET or PEN film is preferably used to form a film. Biaxial stretching may be sequential or simultaneous biaxial stretching.
The stretching method may be a known method. The stretching temperature is generally 50 to 120xc2x0 C. and the draw ratio in a longitudinal direction is 1.1 to 6.5 times, preferably 1.5 to 6.0 times, more preferably 2.5 to 5.0 times. When biaxial stretching is carried out, the draw ratio in a transverse direction is 1.1 to 6.5 times, preferably 2.5 to 6.0 times, more preferably 2.8 to 5.2 times. The film may be stretched in both longitudinal and transverse directions simultaneously. After the film is stretched in longitudinal and transverse directions, it may be further stretched in longitudinal and transverse directions.
After stretching, the film is preferably heat set. The film obtained by stretching is preferably heat set at 125 to 180xc2x0 C., preferably 130 to 175xc2x0 C. for 1 to 100 seconds.
According to the present invention, as described above, there is also provided a laminated polyester film comprising the aromatic polyester film of the present invention and another polyester layer formed on at least one side of the aromatic polyester film.
The another polyester layer of the laminated film is formed from a copolymer which satisfies the following expressions (1) to (5):
40xe2x89xa6NDA+TA less than 100xe2x80x83xe2x80x83(1)
0 less than SDxe2x89xa65xe2x80x83xe2x80x83(2)
0xe2x89xa6ODxe2x89xa660xe2x80x83xe2x80x83(3)
40xe2x89xa6EG+TMGxe2x89xa6100xe2x80x83xe2x80x83(4)
0xe2x89xa6BPAOxe2x89xa660xe2x80x83xe2x80x83(5)
wherein NDA, TA, SD and OD are mol % of 2,6-naphthalenedicarboxylic acid, terephthalic acid, aromatic dicarboxylic acid having a sulfonate salt group and another aromatic dicarboxylic acid based on the total of all the dicarboxylic acid components, respectively, and EG, TMG and BPAO are molt of ethylene glycol, tetramethylene glycol and a bisphenol A adduct with a lower alkylene oxide based on the total of all the diol components, respectively.
The above copolymer comprises 2,6-naphthalenedicarboxylic acid (NDA) and terephthalic acid (TA) in a total amount of 40 mol % or more and less than 10 mol % (formula (1)), an aromatic dicarboxylic acid having a sulfonate salt group in an amount of more than 0 mol % and 5 mol % or less (formula (2)), and an aromatic dicarboxylic acid other than the above dicarboxylic acid in an amount of 0 mol % or more and 60 mol % or less (formula (3)) as acid components constituting the copolymer, and ethylene glycol (EG) and tetramethylene glycol (TMG) in a total amount of 40 mol % or more and 100 mol % or less (formula (4)) and a bisphenol A adduct with a lower alkylene oxide (BPAO) in an amount of 0 mol % or more and 60 mol % or less (formula (5)) as glycol components.
Out of the acid components, 2,6-naphthalenedicarboxylic acid and terephthalic acid may be mixed together or used alone. When 2,6-naphthalenedicarboxylic acid is used alone and the amount of 2,6-naphthalenedicarboxylic acid is smaller than 40 mol %, the anti-block properties of the obtained film lower disadvantageously. When the amount is larger than 90 mol % and the polyester is to be dispersed in water to prepare a coating, the dissolution of the polyester in a hydrophilic organic solvent becomes difficult, thereby making it difficult to disperse it in water. In this case, the copolymerization of a glycol component is effective in improving non-crystallinity. However, when the amount of 2,6-naphthalenedicarboxylic acid is 100 mol %, even if glycol components are copolymerized, the obtained polyester does not dissolve in a hydrophilic organic solvent any longer.
The amounts of 2,6-naphthalenedicarboxylic acid (NDA) and terephthalic acid (TA) as components to be copolymerized are preferably selected to satisfy requirements for a laminated film and to ensure that adhesion and anti-block properties required for a final product and affinity with an aromatic polyester film to be coated become satisfactory.
For example, when the laminated polyester film is a double-layer film consisting of a poly(trimethylene 2,6-naphthalene dicarboxylate) layer and a copolyester layer, the amounts must be selected to ensure that adhesion, anti-block properties and affinity between poly(trimethylene-2,6-naphthalene dicarboxylate) and the copolymer become satisfactory.
The total amount of 2,6-naphthalenedicarboxylic acid and terephthalic acid is preferably 40 to 98 mol %, more preferably 40 to 95 mol %. The amount of 2,6-naphthalenedicarboxylic acid is preferably 98 mol % or less. The amount of terephthalic acid is preferably 70 to 99 mol %, more preferably 80 to 98 mol %.
The copolymer which does not satisfy the above conditions is unsatisfactory in terms of adhesion and anti-block properties.
When the amount of the aromatic dicarboxylic acid (SD) having a sulfonate salt group is 0 mol %, the hydrophilic nature of the obtained copolymer lowers, thereby making it difficult to disperse it in water. When the amount is larger than 5 mol %, the anti-block properties of the obtained film lower disadvantageously. The amount of the aromatic dicarboxylic acid (SD) having a sulfonate salt group is referably 0.001 to 4.7 mol %, more preferably 0.05 to 4.5 mol %.
Preferred examples of the aromatic dicarboxylic acid (SD) having a sulfonate salt group include 5-sodium sulfoisophthalic acid, 5-potassium sulfoisophthalic acid, 5-lithium sulfoisophthalic acid, 5-phosphonium sulfoisophthalic acid and the like.
The acid components of the above copolymer in the present invention include 2,6-naphthalenedicarboxylic acid and an aromatic dicarboxylic acid having a sulfonate salt group in the above amounts. Another aromatic dicarboxylic acid other than the above aromatic dicarboxylic acid, such as isophthalic acid, phthalic acid, bisphenyldicarboxylic acid or lower alkyl ester thereof may be used in combination with these. Out of these aromatic dicarboxylic acids, isophthalic acid and methyl esters thereof are particularly preferred.
Further, the amount of the another aromatic dicarboxylic acid based on the total of all the acid components of the copolymer in the present invention is selected according to the required physical properties of a film.
The total amount of ethylene glycol (EG) and tetramethylene glycol (TMG) out of the glycol components of the above copolymer in the present invention is preferably 40 to 100 mol % and the amount of the bisphenol A adduct with a lower alkylene oxide (BPEO) is 0 to 60 mol %.
When the total amount of ethylene glycol (EG) and tetramethylene glycol (TMG) is smaller than 40 mol %, the adhesion and anti-block properties of the obtained film lower disadvantageously. The total amount is more preferably 50 to 90 mol %.
The amount of ethylene glycol (EG) is preferably 60 to 95 mol %, more preferably 70 to 90 mol %.
The amount of tetramethylene glycol (TMG) is preferably 60 to 95 mol %, more preferably 70 to 90 mol %.
The bisphenol A adduct with a lower alkylene oxide (BPAO) and ethylene glycol must be used in combination as the glycol components of the above copolymer.
The bisphenol A adduct with a lower alkylene oxide (BPAO) is a compound represented by the following formula: 
wherein R is a hydrogen atom or lower alkyl group having 1 to 5 carbon atoms, Ar is a phenylene group or group obtained by substituting at least one of four hydrogen atoms on a ring with a lower alkyl, and m and n are natural numbers with the proviso that m+n is 2 to 10.
The use of this compound is effective in improving the water dispersibility of the obtained copolymer.
In the above formula, examples of the lower alkyl represented by R include methyl, ethyl, propyl, butyl, pentyl and the like, out of which methyl is particularly preferred. Examples of the lower alkyl substituent for the hydrogen on the ring of Ar include methyl, ethyl, propyl, butyl, pentyl and the like, out of which methyl is particularly preferred. Ar is preferably a phenylene group or monomethyl-substituted phenylene group, out of which a phenylene group is particularly preferred.
Examples of the bisphenol A adduct with a lower alkylene oxide (BPAO) include bisphenol A adducts with ethylene oxide, propylene oxide, butadiene oxide and the like. Bisphenol A adducts with ethylene oxide and propylene oxide are particularly preferred. When m+n is large, the anti-block properties of the polymer lower. m+n is preferably 10 or less, more preferably 8 or less, the most preferably 4.
The glycol components of the copolymer include ethylene glycol and the bisphenol A adduct with a lower alkylene oxide in the above amounts. Another aliphatic or alicyclic glycol other than these may further be used in an amount of less than 10 mol %. Preferred examples of the another aliphatic or alicyclic glycol include 1,4-butanediol, 1,4-cyclohexane dimethanol and the like.
The intrinsic viscosity of the above copolymer is preferably 0.4 to 0.8, more preferably 0.5 to 0.7. The intrinsic viscosity is measured in o-chlorophenol at 35xc2x0 C.
The method of producing the copolymer in the present invention may be any conventionally known method or method which has been accumulated by the industry and is capable of producing the copolymer efficiently.
A preferred production method is to carry out an ester exchange reaction between an ester derivative of 2,6-naphthalenedicarboxylic acid and an aliphatic glycol by heating in the presence of an ester exchange catalyst and a polycondensation reaction in the presence of a polycondensation catalyst.
Specifically, 2,6-naphthalenedicarboxylic acid or ester forming derivative thereof, isophthalic acid or ester forming derivative thereof, and 5-sodium sulfoisophthalic acid or ester forming derivative thereof are reacted with ethylene glycol and a bisphenol adduct with propylene oxide to form a monomer or oligomer which is then polycondensed under vacuum to produce a copolymer having a predetermined intrinsic viscosity. At this point, catalysts for promoting the reactions, such as an esterification catalyst, ester exchange catalyst and polycondensation catalyst, and various stabilizers and additives may be added.
In the present invention, any conventionally known method or method which has been accumulated by the industry and is capable of producing the copolymer efficiently may be used without restriction to laminate a copolymer constituting at least one surface layer.
For example, the copolymer constituting at least one surface layer is dispersed in water or an organic solvent and the resulting dispersion is coated on the aromatic polyester film of the present invention to form a laminated film.
Particularly when a polyester water dispersion is to be coated on the aromatic polyester film of the present invention, the coating solution may be produced by the following method, for example.
Preferably, the copolymer has a solubility in 1 liter of water at 20xc2x0 C. of 20 g or more and a boiling point of 100xc2x0 C. or less and dissolves in a hydrophilic organic solvent which boils together with water at 100xc2x0 C. or less. Examples of the organic solvent include dioxane, acetone, tetrahydrofuran, methyl ethyl ketone and the like. A small amount of a surfactant such as dodecylbenzenesulfonic acid may be added to the solution. The copolymer is dissolved in a hydrophilic organic solvent, water is added to the solution under agitation, preferably high-speed agitation by heating to prepare a blue white or semitranslucent dispersion. A blue white or semitranslucent dispersion may also be prepared by adding the organic solution to water under agitation.
When the hydrophilic organic solvent is distilled off from the obtained dispersion at normal pressure or reduced pressure, the copolymer water dispersion of interest is obtained. When the copolymer is dissolved in a hydrophilic organic solvent which boils together with water, the copolymer is preferably dispersed in a slightly large amount of water in consideration of a reduction in the amount of water (co-boiling part) because water co-boils at the time of distilling off the organic solvent.
Further, when the solid content after distillation is higher than 40 wt %, the re-agglomeration of copolyester fine particles dispersed in water readily occurs and the stability of the water dispersion lowers. Therefore, the solid content after distillation is preferably set to 40wt % or less. There is no lower limit to solid content but when the solid content is too low, the time required for drying becomes too long. Therefore, the solid content is preferably 0.1 wt % or more, more preferably 5 wt % or more and 30 wt % or less.
The average particle diameter of the copolymer fine particles is generally 1 xcexcm or less, preferably 0.8 xcexcm or less.
The thus obtained water dispersion of the copolymer constituting at least one surface layer is coated on one side or both sides of the aromatic polyester film of the present invention and dried to provide useful characteristic properties to the film.
The above dispersion may contain a surfactant such as an anionic surfactant or nonionic surfactant as required at the time of coating. The effective surfactant can reduce the surface tension of the polyester to 40 dyne/cm or less and promote the wetting of the polyester film. Most of known surfactants may be used. Examples of the surfactant include polyoxyethylene alkyl phenyl ethers, polyoxyethylene fatty acid esters, sorbitan fatty acid esters, glycerin fatty acid esters, fatty acid metal soap, alkyl sulfuric acid salts, alkyl sulfonic acid salts, alkyl sulfosuccinic acid salts, quaternary ammonium chloride, alkylamine hydrochlorides, sodium dodecylbenzene sulfonates and the like.
The copolymer water dispersion may contain an antistatic agent, filler, ultraviolet absorber, lubricant, colorant and the like as required.
Any conventionally known method or method which has been accumulated by the industry and is capable of producing a film efficiently may be used without restriction to produce the laminated polyester film of the present invention.
The laminated polyester film of the present invention may be any one of an unstretched film, uniaxially oriented film and biaxially oriented film, out of which a biaxially oriented film is preferred.
A description is specifically given of a laminated film consisting of two layers.
The step of coating the above copolymer water dispersion on the aromatic polyester film of the present invention can be optionally selected. The copolymer water dispersion is coated on the unstretched film or uniaxially oriented film of the aromatic polyester of the present invention, dried by heating and further stretched, or is coated on the biaxially oriented film of the aromatic polyester of the present invention and dried. Out of these, the dispersion is preferably coated on the uniaxially oriented film.
Coating may be carried out by a commonly used method such as kiss coating, reverse coating, gravure coating, die coating or the like. The amount of coating is preferably 0.01 to 5 xcexcm (dry), more preferably 0.01 to 2 xcexcm (dry), the most preferably 0.01 to 0.3 xcexcm (dry) as the final thickness.
The laminated polyester film of the present invention preferably has a total of Young""s moduli in longitudinal and transverse directions of 400 kg/mm2 or more when it is a biaxially oriented film. When the total of Young""s moduli is below the above range, the strength of the obtained film becomes insufficient disadvantageously. A film having a total of Young""s moduli in both longitudinal and transverse directions of more than 700 kg/mm2 is inferior in delamination resistance. The total of Young""s moduli is more preferably 450 to 650 kg/mm2.
Since the thus obtained laminated polyester film has excellent gas barrier properties and high adhesive force as well as excellent heat resistance, water resistance and anti-block properties, it is useful as a food packing material, printing material, graphic material, photosensitive material or the like.
Out of aromatic polyesters constituting the above aromatic polyester film of the present invention, an aromatic polyester comprising 2,6-naphthalenedicarboxylic acid as the main dicarboxylic acid component, 1,3-propanediol as the main diol component and a sulfonic acid quaternary phosphonium salt having an ester forming functional group in an amount of 0.1 to 45 mmol % based on the total of all the dicarboxylic acid components is novel and provided by the present invention.
The above aromatic polyester can be a copolymer whose main dicarboxylic acid component is substantially 2,6-naphthalenedicarboxylic acid and whose main diol component is substantially 1,3-propanediol and which comprises, as a copolymerized composition, at least one compound selected from dicarboxylic acids other than 2,6-naphthalenedicarboxylic acid and diols other than 1,3-propanediol in an amount of 30 mol % or less based on the total of all the dicarboxylic acid components. The other dicarboxylic acids and the other diols have already been listed above. It should be understood that the above description is applied to what is not described of this aromatic polyester herein.
The quaternary phosphonium salt having an ester forming functional group is preferably a compound represented by the following formula: 
wherein A is a group having an aromatic ring with 6 to 18 carbon atoms, Y1 and Y2 are the same or different and each a hydrogen atom or ester forming functional group (Y1 and Y2 cannot be a hydrogen atom at the same time), n is 1 or 2, and R1, R2, R3 and R4 are the same or different and each an alkyl group having 1 to 18 carbon atoms, benzyl group or aryl group having 6 to 12 carbon atoms.
In the above formula, A is a group having an aromatic ring with 6 to 18 carbon atoms, preferably a group having a benzene skeleton, naphthalene skeleton or biphenyl skeleton. The aromatic ring may be substituted by an alkyl group having 1 to 12 carbon atoms in addition to Y1, Y2 and a sulfonic acid quaternary phosphonium base. Y1 and Y2 are a hydrogen atom or ester forming functional group such as xe2x80x94COOH, xe2x80x94COORxe2x80x2, xe2x80x94OCORxe2x80x2, xe2x80x94(CH2)nOH and xe2x80x94(OCH2)nOH. In these groups, Rxe2x80x2 is a lower alkyl group having 1 to 4 carbon atoms or phenyl group, and n is an integer of 1 to 10. Preferred examples of Rxe2x80x2 include methyl, ethyl, n-propyl, iso-propyl, n-butyl and the like. R1, R2, R3 and R4 constituting the sulfonic acid quaternary phosphonium base are the same or different. Examples of the alkyl group having 1 to 18 carbon atoms include methyl, ethyl, propyl, butyl, dodecyl, steryl and the like. Examples of the aryl group having 6 to 12 carbon atoms include phenyl, naphthyl, biphenyl and the like.
Preferred examples of the above sulfonic acid quaternary phosphonium salt include tetrabutylphosphonium 3,5-dicarboxybenzene sulfonate, ethyltributylphosphonium 3,5-dicarboxybenzene sulfonate, behzyltributylphosphonium 3,5-dicarboxybenzene sulfonate, phenyltributylphosphonium 3,5-dicarboxybenzene sulfonate, tetraphenylphosphonium 3,5-dicarboxybenzene sulfonate, butyltriphenylphosphonium 3,5-dicarboxybenzene sulfonate, tetrabutylphosphonium 3,5-dicarbomethoxybenzene sulfonate, ethyltributylphosphonium 3,5-dicarbomethoxybenzene sulfonate, benzyltributylphosphonium 3,5-dicarbomethoxybenzene sulfonate, phenyltributylphosphonium 3,5-dicarbomethoxybenzene sulfonate, tetrabutylphosphonium 3,5-di(xcex2-hydroxyethoxycarbonyl)benzene sulfonate, tetraphenylphosphonium 3,5-di(xcex2-hydroxyethoxycarbonyl)benzene sulfonate, tetrabutylphosphonium 3-dicarboxybenzene sulfonate, tetraphenylphosphonium 3-dicarboxybenzene sulfonate, tetrabutylphosphonium 3-di(xcex2-hydroxyethoxycarbonyl)benzene sulfonate tetraphenylphosphonium 3-di(xcex2-hydroxyethoxycarbonyl)benzene sulfonate, tetrabutylphosphonium 4-di(xcex2-hydroxyethoxycarbonyl)benzene sulfonate, bisphenol A-3,3-di(tetrabutylphosphonium sulfonate), tetrabutylphosphonium 2,6-dicarboxynaphthalene-4-sulfonate and the like. The above sulfonic acid quaternary phosphonium salts may be used alone or in combination of two or more.
In the present invention, the sulfonic acid quaternary phosphonium salt is contained in an amount of 0.1 to 45 mmol % based on the total of all the dicarboxylic acids, shows an AC volume resistivity of 2.0xc3x97108 xcexa9cm or less when the polyester is molten, can provide a sufficient amount of charge for sticking the polyester to a cooling drum which rotates relatively fast and can improve the film forming speed which is one of the objects of the present invention. The above aromatic polyester of the present invention can be produced by any known method.
To copolymerize the above sulfonic acid quaternary phosphonium salt with the aromatic polyester, it may be added to a reaction system in any stage before the synthesis of the aromatic polyester is completed, or may be fed to a vented double-screw kneading extruder together with the aromatic polyester to be melt kneaded after the synthesis of the aromatic polyester is completed.
The sulfonic acid quaternary phosphonium salt which is detected after 2 hours of immersion in a 50% ethanol solution at 250xc2x0 F. (121xc2x0 C.) is preferably contained in the aromatic polyester of the present invention in an amount of 1 ppm or less. When the amount of the detected sulfonic acid quaternary phosphonium salt is more than 1 ppm, the obtained film is not preferred as a food packing material. To adjust the amount of the detected sulfonic acid quaternary phosphonium salt to 1 ppm or less, the sulfonic acid quaternary phosphonium salt may be added in the stage of synthesizing the polyester or at least 3 minutes after the synthesis of the polyester to ensure that the temperature in the reaction system becomes 240xc2x0 C. or more, when the polyester is prepared.
The above aromatic polyester of the present invention may contain an antimony compound in an amount of 70 to 400 ppm in terms of antimony atoms, a titanium compound in an amount of 15 to 300 ppm in terms of titanium atoms and a germanium compound in an amount of 30 to 400 ppm in terms of germanium atoms.
The above metal compounds are used as polymerization catalysts for the aromatic polyester.
The antimony compound used as a polymerization catalyst is not particularly limited and any Sb compound having polymerization catalytic activity may be used. Examples of the antimony compound include oxides such as antimony trioxide, antimony tetraoxide and antimony pentoxide, halides such as antimony trichloride and antimony tribromide, acid salts such as antimony acetate, alcoholates such as antimony glycolate, and the like. Out of which, oxides are preferred and antimony trioxide is particularly preferred.
The antimony compound is contained in an amount of preferably 70 to 400 ppm, particularly preferably 100 to 350 ppm in terms of antimony atoms. When the amount of antimony is smaller than 70 ppm, sufficient polymerization activity cannot be obtained, which is not preferred for the production of a polyester. When the amount of antimony is larger than 400 ppm, the obtained polyester becomes blackish and the antimony catalyst residue is contained in the polyester as foreign matter.
The titanium compound used as a polymerization catalyst is not particularly limited and any titanium compound having polymerization catalytic activity may be used. Examples of the titanium compound include titanium tetrabutoxide, titanium tetrapropoxide, titanium tetraethoxide, titanium isopropoxyoctylene glycol, titanium butoxyoctylene glycol and reaction mixtures of these and acid anhydrides. Out of these, titanium tetrabutoxide or a reaction product of it and an acid anhydride is particularly preferred from the viewpoints of polymerization activity and cost.
The titanium compound is contained in an amount of preferably 15 to 300 ppm, particularly preferably 20 to 100 ppm in terms of titanium atoms. When the amount of titanium is smaller than 15 ppm, sufficient polymerization activity cannot be obtained, which is not preferred for the production of a polyester. When the amount of titanium is larger than 300 ppm, the obtained polyester becomes yellowish and deteriorates in heat resistance disadvantageously.
The germanium compound used as a polymerization catalyst is not particularly limited and any germanium compound having polymerization catalytic activity may be used. Germanium dioxide is preferred as the germanium compound. So-called amorphous germanium having no crystal form is particularly preferred because it can reduce the number of particles which separate out in the polymer.
The amount of the germanium compound added is preferably such that the amount of a germanium compound contained in the produced polyester should be 30 to 400 ppm, particularly preferably 40 to 350 ppm in terms of germanium atoms. When the amount of germanium contained in the polyester is smaller than 30 ppm, sufficient polymerization activity cannot be obtained and it may be difficult to produce the polyester. When the amount of germanium contained in the polyester is larger than 400 ppm, the color of the obtained polyester may worsen or the heat resistance thereof may lower.
The aromatic polyester of the present invention preferably contains no more than 50 foreign substances of 10 xcexcm or more in size per 1 g of the aromatic polyester. The number of foreign substances per 1 g of the aromatic polyester is more preferably 30 or less, particularly preferably 10 or less. When the number of foreign substances of 10 xcexcm or more in size is larger than 50 and, for example, a biaxially oriented film is formed from the aromatic polyester containing these foreign substances, portions around the foreign substances are stretched, thereby forming voids around the foreign substances with a high probability of producing large film surface defects. To reduce the number of foreign substances of 10 xcexcm or more in size to 50 or less, the amount of metallic Sb derived from the Sb compound catalyst remaining in the polyester must be reduced to 70 to 400 ppm.
The L value and b value measured by an Lab method of the above aromatic polyester of the present invention preferably satisfy the following expressions (6) and (7):
65xe2x89xa6Lxe2x88x92bxe2x80x83xe2x80x83(6)
bxe2x89xa610xe2x80x83xe2x80x83(7)
wherein L and b are L and b values measured by a color difference meter.
The value Lxe2x88x92b is more preferably 70 or more. The b value is preferably 8 or less, more preferably 6 or less. The greater the L value, the more the whiteness improves. The greater the b value, the more the yellow tint increases. When the polyester does not satisfy the above expressions, the film becomes yellowish by heat history at the time of forming a film by melt extrusion. Therefore, when it is used as a packing film, its color becomes worse and cuts down consumers"" purchase desire. Means of controlling the color of the polyester to satisfy the above expressions is not particularly limited. The above expressions can be satisfied, for example, by suitably controlling the amount of titanium atoms derived from the titanium compound remaining in the polyester to 15 to 300 ppm, polymerization temperature and polymerization time.
According to the present invention, there is provided a polyester composition comprising the above aromatic polyester of the present invention and another aromatic polyester. That is, the polyester composition provided by the present invention comprises the aromatic polyester of the present invention in an amount of 60 wt % or more and another aromatic polyester in an amount of 40 wt % or less based on the total of the aromatic polyester of the present invention and the another aromatic polyester.
Examples of the another aromatic polyester include polyethylene terephthalate, polyethylene-2,6-naphthalene dicarboxylate, polytetramethylene terephthalate, polytetramethylene-2,6-naphthalene dicarboxylate, polyhexamethylene terephthalate, polyhexamethylene-2,6-naphthalene dicarboxylate and copolymers thereof. These another aromatic polyesters may be used alone or in combination of two or more. When the amount of the another aromatic polyester is larger than 40 wt %, the obtained composition has low light resistance and the obtained film has low transparency. The amount of the another aromatic polyester is preferably 35 wt % or less, more preferably 30 wt % or less.
The above polyester composition of the present invention preferably has an intrinsic viscosity measured at 35xc2x0 C. in a mixed solvent of phenol/tetrachloroethane (weight ratio of 6:4) of 0.4 to 1.5. When the intrinsic viscosity is lower than 0.4, the obtained film is unsatisfactory in terms of mechanical properties and when the intrinsic viscosity is higher than 1.5, moldability stretchability becomes insufficient disadvantageously. The intrinsic viscosity is preferably in the range of 0.45 to 1.3, more preferably 0.5 to 1.1.
The polyester composition of the present invention may contain such additives as a lubricant, pigment, dye, antioxidant, light stabilizer, heat stabilizer, light screen, delustering agent and the like as required. A lubricant is particularly effective in providing slipperiness at the time of forming a film.
The method of blending the aromatic polyester of the present invention and another aromatic polyester to produce the polyester composition of the present invention is not particularly limited. Preferred examples of the method include one which the another aromatic polyester is added before the completion of the polymerization reaction of the aromatic polyester of the present invention and the resulting mixture is chipped, one in which the aromatic polyester of the present invention and another aromatic polyester are kneaded together with a melt kneader such as a single-axis or double-axis kneader and chipped, and one in which they are melt kneaded together at the time of forming a film and formed into a film directly. When the melt kneader is used, blended chips may be melt kneaded, or two or more of the above polymers may be supplied into a kneader equipped with a quantitative feeder quantitatively to be melt kneaded together.
Finally, according to the present invention, there is provided an antifungal polyester composition comprising either one of the aromatic polyester of the present invention and the aromatic polyester composition of the present invention and an inorganic anti-fungus agent in an amount of 0.1 to 10 wt % based on the aromatic polyester of the present invention or the aromatic polyester composition of the present invention.
The average particle diameter of the inorganic anti-fungus agent is preferably 0.2 to 7 xcexcm, more preferably 0.4 to 5 xcexcm. The content of the inorganic anti-fungus agent is preferably 0.2 to 7 wt %, more preferably 0.3 to 5 wt %.
An anti-fungus agent which is relatively inexpensive, nontoxic or almost nontoxic, has a high antifungal effect, is insoluble or hardly soluble in water or an organic solvent and does not cause an environmental pollution problem is preferred as the anti-fungus agent.
The average particle diameter is calculated from the following equation by depositing a metal on the surface of each particle and obtaining an area circle equivalent diameter from an image magnified 10,000 to 30,000 times by an electron microscope.
average particle diameter=total of area circle equivalent diameters of measured particles/number of measured particles
When the average particle diameter is smaller than 0.1 xcexcm, the agglomeration of particles occurs, thereby preventing the formation of a film, and when the average particle diameter is larger than 10 xcexcm, pin holes are formed or the film is broken in some cases.
When the amount of the anti-fungus agent is smaller than 0.1 wt %, antifungal properties are not developed and when the amount of the anti-fungus agent is larger than 10 wt %, the polyester film becomes cloudy and not transparent.
To further improve the dispersibility and affinity of the anti-fungus agent with the polyester to achieve transparency, an anti-fungus agent whose surface is treated with an anionic surfactant, aluminum- or titanium-based coupling agent or fatty acid ester of a polyhydric alcohol by a commonly used method may be used.
To contain the anti-fungus agent in the above polyester, various methods may be used. Typical methods are given below.
(a) An anti-fungus agent is added before the completion of an ester exchange or esterification reaction at the time of synthesizing a polyester or before a polycondensation reaction.
(b) An anti-fungus agent is added to a polyester and melt kneaded with the polyester.
(c) A master batch containing an anti-fungus agent in a high concentration is prepared and added to contain a predetermined amount of the anti-fungus agent in the polyester in the above methods (a) and (b). Out of these, the method (a) is the most preferred.
Inorganic anti-fungus agents include inorganic compounds (such as zeolite, zirconium phosphate, montmorillonite, hydroxyapatite, phosphoric acid complex salts, tripolyphosphates, magnesium aluminosilicate, calcium silicate, titanium oxide, silica gel, melting glass and the like) carrying metal ions (such as silver, copper, zinc, tin, lead, bismuth, cadmium, chromium, mercury and the like) and/or complex ions thereof (such as silver thiosulfate ions and the like), and composite metal oxides containing at least two metal elements (such as zinc, copper, magnesium, calcium and the like). Out of these, inorganic compounds carrying a silver ion as a metal ion and/or composite metal oxides are particularly preferred because they have antifungal properties and rarely causes environmental pollution.
An anti-fungus agent containing a composite metal oxide as an effective ingredient is preferably an oxide solid solution represented by the following formula:
[(A1)x(A2)1xe2x88x92x]O
wherein
A1 is a divalent metal selected from Zn and/or Cu,
A2 is also a divalent metal selected from Mg and/or Ca, and
X is an number which satisfies 0.01xe2x89xa6X less than 0.5.
When a metal other than those is used, the obtained anti-fungus agent deteriorates in antifungal properties and environmental pollution disadvantageously. When the proportion of A1 in the formula is smaller than. 0.01, sufficient antifungal properties cannot be obtained and when the proportion of A1 is 0.5 or more, it foams disadvantageously at the time of adding it to the polyester resin.
The polyester resin composition of the present invention is advantageously formed into a film, particularly a packing film. The total haze of the obtained film is preferably 0.1 to 20%.
When the total haze is smaller than 0.1%, the film loses appropriate friction and workability, thereby reducing productivity. When the total haze is larger than 20%, the film loses transparency and shows no design when the back of the film is printed.
The total haze of the film is measured in accordance with JIS-K7105 and obtained from the following expression:
total haze (%)=(Td/Tt)xc3x97100
wherein Td is a diffuse transmission (%) and Tt is a total light transmission (%).
To provide appropriate friction and workability to a film, inert fine particles are preferably contained in the anti-fungus agent in limits that satisfy the above range. Examples of the inert fine particles include fine particles containing the IIA, IIB, IVA and IVB elements of the periodic table (such as kaolin, alumina, titanium oxide, calcium carbonate and silicon dioxide), and polymer fine particles having high heat resistance such as silicone resin and crosslinked polystyrene.
The average particle diameter of the inert fine particles is preferably in the range of 0.01 to 5.0 xcexcm, more preferably 0.1 to 3.0 xcexcm.
The amount of the inert fine particles is preferably in the range of 0.001 to 2.0 wt %, more preferably 0.01 to 1.0 wt %.